1. Field of the Invention
The invention relates generally to the field of symbol or matrix scanning systems, and more particularly to a system for scanning two-dimensional symbologies, including barcodes, (e.g., portable data files) using a one-dimensional scanner.
2. Description of the Related Art
Barcode scanning systems are finding an ever-increasing number of uses and applications. For example, barcoding may be utilized for inventory and warehousing applications, as well as with point of sale terminals. Many different types and complexities of barcodes systems are in use today. A basic barcode symbol scanning system consists of a barcode scanner, a decoder and a computer. The scanner and decoder are utilized to retrieve information from barcodes for use by the computer system.
As part of a barcode reading system, a decoder can be defined as an electronic package that receives a signal from the scanner, performs an algorithm to interpret the signal into meaningful data, and provides the data to other devices of the system. There are 3 main types of decoders: wedge decoders, serial decoders and software decoders. Wedge decoders are external devices that generally wedge between a keyboard and terminal. With keyboard wedge decoders, the data appears as though it was manually typed or keyed directly into the computer. Serial decoders are also external devices that connect into a communications port of the personal computer. Likewise, expensive decoded scanners (i.e., scanners in which the decoder is integrated, usually into the handle of the scanner) usually connect via a keyboard wedge or via a serial port.
Software decoders provide decoding functionality in software executed on a host computer. Many input devices can be used in conjunction with an adapter to plug directly into the serial port of a computer using a software decoder. Unlike software decoders, wedge decoders and serial decoders generally cannot be upgraded to support new symbologies and are thus limited with respect to future capabilities.
Many different types of scanning devices are available. Scanning devices include wands, charge coupled device (CCD) scanners and laser scanners. Wand scanners tend to be the least expensive, followed by CCD scanners and laser scanners (the most expensive). Most scanning devices use a light emitting diode (LED) and a photo detector to scan barcodes. The light generated from the LED falls on the barcodes and is absorbed by the printed bars and reflected by the white spaces. The photodetector senses the reflected light and electro-optically converts the reflected light into a signal. The digitized signal is then sent to a decoder and converted into ASCII or other characters.
Currently, there are more than 400 barcode symbologies in use. Each character in the barcode symbol is generally represented by a series of bars and spaces. Typically, the barcode symbol includes a quiet zone, start code or pattern, data characters, stop code and trailing quiet zone. Many symbologies support check digit(s) to ensure data integrity. With such symbologies, the check digit(s) is usually located before the stop code. A xe2x80x9csymbolxe2x80x9d is a combination of barcode characters (including the start/stop codes, quiet zones, data characters and check characters required by a particular symbology) that forms a complete, scannable entity.
Briefly, a scanning system according to the preferred embodiment of the invention utilizes an inexpensive one-dimensional scanner connected to a serial port of a computer system via an adapter. The adapter functions to convert and remap the scanners TTL signals and to pass raw or undecoded scan data to the serial port of the computer system. The serial port pins are thus used in a non-traditional manner for communicating scanned images of a two-dimensional barcode symbol, or other matrix symbologies, to the computer system. A unique software decoder residing in the computer system then performs image decoding.
In operation, the one-dimensional scanner scans a two-dimensional symbol or matrix, the resulting undecoded data stream is decoded by the software decoder. The software decoder performs a series of iterative steps in which the data stream provided the scanner is sampled and converted to symbol elements. Next, symbol characters are derived from the elements, and a symbol matrix is constructed. Optional error detection and correction procedures may also be performed to construct the finalized decoded barcode symbol. The present invention thus obviates the need for expensive scanning and decoding hardware for decoding two-dimensional symbols.